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Question on Evolution; Speciation

On the tiny lord howe island, 600 miles east of australia, there are two species of palm which seem, from DNA analysis, to be descended from one original species.

Factors involved in this speciation on this tiny island include:
1 - linkage of genes for soil tolerance and flowering time
2 - variation in flowering time
3 - variation of soil tolerance
4 - variation of soil types on the island

What is the correct sequence to explain this speciation?

A. 3 -> 4 -> 1 -> 2
B. 4 -> 3 -> 2 -> 1

Guys, what is the answer and why??

Reply 1

Christina1999H

The answer is B: because the soil type is the selection pressure, and the plant's tolerance is dependent on the soil type..

If flowering is dependent on soil type tolerance, then the two different trees will pollinate at different times:

If tree type A likes soil type a, it could bloom in the August.
Tree type B likes soil type b so only grows in that area of the island where that soil type is present, and the variation in flowering means it will bloom at a different time, for example June.

Because the flowering time does not overlap, the trees are reproductively isolated leading to different genetic material over time

Hope that makes sense?

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